[davidgto]

I have a center tripwr carb that wants to stick coming off the idle position, but only after the engine is at operating temperature. When it is first started ,on a cold start, the accelerator pedal opens and closes carb as it should, but after warming up , it has the hard spot just coming off idle.. Problem is the carb, not the cable. Any thoughts on the remedy?

[Dick Boneske]

I've learned through the years that this problem is caused by too little clearance between the throttle shaft and bore through the base. The symptom is exactly as you described. Adding more spring pressure to return the throttle makes the car difficult to drive.

There needs to be .003" clearance between the bore and the shaft. Buy a long 8 mm drill. 8 mm is .315", which gives you .003" clearance with the .3125" (5/16") throttle shaft.

I've been through this problem many times, so, believe me, more clearance is the answer.

[Kenth]

If your new pump seal are of the old black style, this would be your problem.
They swell and WILL stick in the bore.

[Dick Boneske]

Kenth’s suggestion is ok, but your symptoms point toward what I described—too little clearance. Otherwise, the problem would not be heat related.

I forgot to mention—When looking at the throttle base, be sure the steel lever has at least 1/32” clearance between it and the cast iron base. This can also cause a hestrelated sticking problem.

[aogmitch]

Mine started doing the same thing last year. Added some extra spring for now, but it is in the shaft once warms up. Annoying as heck.

[Dick Boneske]

Fix is easy. Remove the carb. Remove the throttle body. Remove the throttle plates.

Run a long 8 mm drill through the throttle shaft bore. Blow out the chips.

Re-assemble., but be sure to position the throttle lever to clear the cast iron base by at least 1/32” before tightening the throttle plate screws.

If you don’t have the tools or skill to do this. DM me, and I’ll do it for you if you send me the carb. I would also replace the accelerator pump and needle/seat while it’s apart.

[aogmitch]

Getting ready to remove the intake and fix the coolant leak at the timing cover. Will take care of the carb when its off. Have access to good .315 reamers.

[Dick Boneske]

That will work fine.

[ejgoat]

would this cause a vacuum leak around the shaft?

[Dick Boneske]

Are you asking if .003” throttle shaft clearance will cause a vacuum leak? The answer is that leak is insignificant in the operation of the carburetor. Less clearance causes the throttle to stick when hot.